The present invention relates to a silver halide photographic material. More particularly, the invention relates to a silver halide photographic material which uses a specified cyan coupler so as to provide a cyan dye image having improved resistance to discoloration both in light and dark places, thereby achieving a balanced discoloration between yellow, magenta and cyan colors.
Silver halide color photographic materials typically comprise a support having formed thereon three silver halide emulsion layers selectively sensitized to have sensitivity to blue, green and red lights. For example, in color negative photographic materials, blue-, green- and red-sensitive silver halide emulsion layers are formed on a support, with the blue-sensitive emulsion layer being positioned on the top and closest to a light source for the purpose of exposure. The blue- and green-sensitive emulsion layers are interposed by a bleachable yellow filter layer which absorbs a blue light transmitted through the blue-sensitive emulsion layer. Other intermediate layers that are intended for achieving certain purposes are disposed between each emulsion layer while a protective layer is formed as the outermost layer. In photographic materials used as color papers, red-, green- and blue-sensitive silver halide emulsion layers are formed on a support, with the red-sensitive emulsion layer being positioned the closest to a light source for the purpose of exposure. As in color negative photographic materials, a UV absorbing layer and other intermediate layers for achieving various purposes are formed, as well as a protective layer. The emulsion layers may be arranged in different orders, and it is also common for each emulsion layer to be replaced by at least two emulsion layers which have substantially the same sensitive region for a particular light but which have different degrees of sensitivity to such light. With all types of silver halide color photographic materials, aromatic primary amine compounds are typically used as colored developing agents so as to develop exposed silver halide grains, and the resulting oxidation product of the color developing agent reacts with a dye forming coupler so as to form a dye image. In order to produce cyan, magenta and yellow dye images, a phenolic or naphtholic cyan coupler, a 5-pyrazolone pyrazolinobenzimidazole, pyrazolotriazole, indazolone or cyanoacetyl magenta coupler and an acylacetamide or benzoylmethane yellow coupler are respectively used. These dye forming couplers are incorporated in sensitive, color photographic emulsion layers.
Silver halide photographic materials bearing the dye images thus formed are stored under exposure to light for an extended period and may experience discoloration. The same problem occurs if the photographic materials are stored in a dark place under certain conditions. The first type of discoloration is generally referred to as "light discoloration" whereas the second type is called "dark discoloration". In order to store color photographic materials semipermanently, the degree of light and dark discoloration should be minimized and the overall balance in the coloration of yellow, magenta and cyan dye images must be held as close as possible to the initial state. However, these three dye images suffer different degrees of light and dark discoloration and, after extended storage, the overall balance in the discoloration of the three colors is upset and quality of the respective dye images is deteriorated.
Two different approaches are being taken in the attempts being made to solve this problem: one is to develop a new coupler capable of forming a dye image that suffers less discoloration, and the other is to develop a new additive capable of preventing undesired discoloration. Methods using the second approach are characterized by incorporating a UV absorber or forming a UV absorbing filter in a color photographic material. However, in order to provide a satisfactory degree of light fastness with a UV absorber, the latter must be used in a fairly large amount, but then the dye image is considerably stained by the UV absorber or the latter forms a precipitate without being completely dissolved in a high-boiling solvent. Another problem is caused by the fact that the UV absorber is degraded if the dye image is exposed to a strong actinic radiation for an extended period, and the deteriorated UV absorber enhances, rather than inhibits, the discoloration of the dye image.
The UV absorber is not effective in preventing discoloration resulting from visible light, so anti-discoloration agents other than UV absorbers have also been proposed. Among such agents that have a phenolic hydroxyl group or a group that is hydrolyzed to form a phenolic hydroxyl group are bisphenols (Japanese Patent Publication Nos. 31256/1973 and 31625/1973), pyrogallol, gallic acid and esters or acyl derivatives thereof (U.S. Pat. No. 3,069,262), 6-hydroxychromans (U.S. Pat. Nos. 3,432,300 and 3,574,627), 5-hydroxychroman derivatives (U.S. Pat. No. 3,573,050) and 6,6'-dihydroxy-bisspirochromans (Japanese Patent Publication No. 20977/1974). However, some of these agents are entirely ineffective against dark discoloration and, in an extreme case, they enhance such dark discoloration although they can effectively inhibit the light discoloration of a dye image. Other agents retain their intended effects for a certain period but during extended storage of the dye image of interest, their effects are rapidly decreased or lost entirely. A strain problem may also be caused by such anti-discoloration agents. Several of such agents are effective against the discoloration of a magenta dye image but they accelerate appreciably the discoloration of a cyan dye image.
Considerable effort is also being made in the art to develop new couplers capable of forming dye images that suffer less discoloration. As already mentioned, in order to ensure extended or semi-permanent storage of formed yellow, magenta and cyan dye images, they must have a good color balance. Even if these dye images are exposed to light for an extended period or if they are stored in a dark place under a hot and humid condition, they should suffer little or no discoloration. However, the degree of light and dark discoloration varies among yellow, magenta and cyan dye images. As for dark discoloration, a cyan dye image is the most vulnerable, then comes a yellow dye image, and a magenta dye image is most resistant. It is worth a particular mention that the degree of discoloration in the cyan dye image is most greater than in the other dye images. As for light discoloration, the cyan dye image is also the most vulnerable and the magenta dye image is the most resistant, assuming a light source having a high content of UV radiation.
It is therefore concluded that in order to retain a good balance in the discoloration of yellow, magenta and cyan colors for an extended period, the light and dark discoloration of a cyan dye image must be reduced to a minimum, and this is why the development of a new type of cyan coupler that is less likely to cause light or dark discoloration is strongly desired.
Conventional cyan couplers such as those shown in Japanese Unexamined Published Patent Application Nos. 37425/1972, 10135/1975, 25228/1975, 112038/1975, 117422/1975, 130441/1975, and U.S. Pat. Nos. 2,369,929, 2,423,730, 2,434,272, 2,474,293 and 2,698,794 easily suffer both light and dark discolorations, and color photographic materials bearing cyan dye images produced from these couplers cannot be stored for an extended period without upsetting the overall balance in the discoloration of yellow, magenta and cyan colors. In order to solve this problem, various other cyan couplers have been studied and 2,5-diacylamino compounds have recently come to be used (see U.S. Pat. No. 2,895,826 and Japanese Unexamined Published Patent Application Nos. 112038/1975, 109630/1978 and 163537/1980). Cyan couplers made of these compounds have an appreciably improved resistance to dark discoloration but are still unsatisfactory in terms of resistance to light discoloration.